msm: rpm_stats: Debugfs support to display master PC stats.

rpm maintains stats on power collapses and the list of active cores
for each master in its msg ram. Provide support to display it
through debugfs.
ex:-
	mount -t debugfs none /data/debug
	cd /data/debug
	cat rpm_master_stats
The above commands will display no of power collapses and active cores
for each master. Sample output on 8960 is below

	KPSS
		num_shutdowns:0
		active_cores:7
			core0
			core1
			core2
	MPSS
		numshutdowns:10
		activecores:0
	LPASS
		numshutdowns:20
		activecores:1
			core0
	RIVA
		numshutdowns:9
		activecores:0
	DSPS
		numshutdowns:90
		activecores:0

L2 cache also consider as another core in the stats.

Signed-off-by: Anji Jonnala <anjir@codeaurora.org>

Change-Id: I570335c11f744663819ab040705fe715183bda8a
Signed-off-by: Neha Pandey <nehap@codeaurora.org>